package com.example.commontools.view.recycleviewadapter;

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Grid分割线
 */
public class EasyGridSpacingItemDecoration extends RecyclerView.ItemDecoration
{

    private int spanCount;

    private int spacing;

    private boolean includeEdge;

    private int headerNum;

    public EasyGridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge, int headerNum)
    {

        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
        this.headerNum = headerNum;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state)
    {

        int position = parent.getChildAdapterPosition(view) - headerNum; // item position

        if (position >= 0)
        {
            int column = position % spanCount; // item column

            if (includeEdge)
            {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

                if (position < spanCount)
                { // top edge
                    outRect.top = spacing;
                }
                outRect.bottom = spacing; // item bottom
            } else
            {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
                if (position >= spanCount)
                {
                    outRect.top = spacing; // item top
                }
            }
        } else
        {
            outRect.left = 0;
            outRect.right = 0;
            outRect.top = 0;
            outRect.bottom = 0;
        }
    }
}
